The present invention relates to a timepiece with minute repeater, comprising an hour rack, a positive-return link between this rack and one end of a driving spring, a manual tensioning lever fixed to the hour rack, an hour-striking cam to limit the degree of tensioning of the driving spring to the number of hours to be struck, a quarter rack, a driving link between the hour rack and the quarter rack, a quarter-striking cam to limit the movement of the quarter rack to the number of quarters to be struck, a minute rack, a driving link between the quarter rack and the minute rack, a minute-striking cam to limit the movement of the minute rack to the number of minutes to be struck, two striking hammers, each connected to a gong, sets of teeth and pallets for selectively activating each of the two striking hammers depending on the time indication to be struck.
Timepieces with minute repeaters of the type mentioned above have been known for a long time. One such mechanism is described in particular on the site www.horlogerie-suisse.com in the Complications section. In that mechanism the hour rack drives one end of the driving spring via a toothed bar meshing with a pinion fixed to the end of the driving spring. This pinion is fixed to an hour ratchet which engages with the hour striking pallet. The quarters are struck by two sets of teeth on the quarter piece and the minutes are struck by a set of ratchet teeth on the minute piece, which is driven by the quarter piece.
For this mechanism to work properly, the various racks must be free, and for this purpose they must be separated from each other by sufficient play to prevent them contacting each other. The sets of striking teeth associated with the various racks have to operate four striking pallets. Consequently, each hammer is activated alternately by two striking pallets. This superposition of members which must be separated by sufficient play to allow them to move freely relative to each other occupies a considerable height. It is for this reason that it becomes difficult to make a thin timepiece with that kind of minute-repeater mechanism, especially a wristwatch, where thickness is a particularly critical factor. In point of fact, a conventional repeater mechanism increases the total thickness of the movement very considerably.